1. Field of the Invention
The present invention relates to disk positioning information writing methods and apparatus, an information recording/reproduction apparatus and a recording medium, and, in particular, to a disk positioning information writing method and apparatus by which even when a positional error of disk positioning information occurs due to so-called asynchronous vibration (NRRO; i.e., non-repeatable runout) in a disk positioning information writing apparatus such as a servo track writer, a positioning error upon recording/reproduction on a disk can be effectively avoided; an information recording/reproduction apparatus carrying out information recording/reproduction on the thus-obtained disk; and a recording medium which is the disk.
2. Description of the Related Art
A ‘servo track’ previously written on a magnetic disk for the purpose of carrying out positioning control of a recording/reproduction head in a magnetic disk apparatus is used to provide disk positioning information.
In the magnetic disk apparatus, positioning of the recording/reproduction head is carried out with the use of the servo track previously written in the magnetic disk as mentioned above. Known servo control methods may be classified into the following two types in terms of a position detecting method from a servo pattern (a servo burst or such) written as the positioning information on the disk.
A first method applies a burst pattern. In this method, the precise position of a head is detected as a result of amplitudes of two sets of burst patterns having phases different by 90°, i.e., four sets of burst patterns being calculated. This method also includes a method in which the number of bursts forming the burst patterns is three phases, six phases, or such, other than the above-mentioned four phases. A second method is to apply a phase pattern. In this method, previously recorded patterns are disposed in such a manner that, along with movement of a head in a track direction, a phase between a reference signal and a position detection signal may linearly shift. Then, by reading this, a detailed position of a head is detected.
As a device to write a servo pattern such as that mentioned above to a disk-shaped medium such as a magnetic disk, a so-called ‘servo track writer’ is known. FIG. 1 shows one example of a common servo track writer. The servo track writer includes a spindle motor having a hard disk drive 100 as a product loaded therein, supporting the same and rotating the same; a clock head 360 previously writing predetermined clock information in a disk-shaped medium 110. The servo track writer reads the clock information therefrom when writing a servo track, and transmitting the same to a servo pattern generator 350. A writing head 130 writes the servo track to the medium; an actuator arm assembly 140 rotateably support the writing head 130; a laser measurement system 320 measures a position of the actuator arm assembly; a positioning controller 340 carries out positioning control of the actuator arm assembly on the side of the hard disk drive via an actuator 330 on the side of the track writer based on position information sent from the laser measurement system; a spindle motor controller 310 controls driving of the spindle motor; and a servo pattern generator 350 generates a servo information pattern to be written in the disk-shaped medium 110 while controlling timing based on the clock information sent from the clock head 360.
In the servo track writer configured above, writing of a servo track is repeated with each rotation of the medium while the writing head is positioned according to a predetermined feeding pitch. This operation is repeated until all the tracks are written.
In this method, the writing head is accurately positioned with respect to the laser measurement system. However, relative positioning with respect to the medium to which the servo track is written is not carried out. Further, a route of a single servo track is determined by the route covered in one pass of servo track writing. Therefore, if NRRO of the spindle motor, an error in positioning of the write head or such occurs, the thus-written servo track does not form a complete concentric circle, and a step occurs in the servo track at the joint part between a writing start and a writing end. When this step is large, a recording/reproduction head cannot stably follow the track in the above-mentioned servo control, and various problems may occur.
In order to solve this problem, Patent Document 1, described later, discloses a method, for example. In this method, a plurality of phases of bursts are written along the direction of the track over a plurality of rotations over that track. As a result of an individual servo track being written over a plurality of rotations, the amount of error occurring due to NRRO from the spindle motor can be averaged over.
Patent Document 2 discloses a method in which a frequency and a phase of NRRO of a spindle motor are measured, and a servo track is written only when a difference in NRRO between a writing start and a writing end is within an acceptable limit.
Patent Document 1:
Japanese Laid-open Patent Application No. 2001-14816
Patent Document 2:
Japanese Laid-open Patent Application No. 2001-14818
Patent Document 3:
Japanese Laid-open Patent Application No. 10-106192
Patent Document 4:
Japanese Laid-open Patent Application No. 2001-28111
However, when a method as disclosed by
Patent Document 1 in which one individual servo track is written over multiple rotations, the time required for writing each servo track is multiplied by the number of the above-mentioned plurality of rotations. As a result, the time required for writing the servo tracks increases remarkably.
In the method of Patent Document 2, although it is not necessary to write a servo track over multiple rotations for each track, as in the method of Patent Document 1, a servo track cannot be written during an acceptable time frame if there is a large amount of NRRO of the spindle motor from the above-mentioned measurement. Therefore, a waiting time occurs, and thus, the time required for writing all the tracks remarkably increases.